The present invention generally relates to musical instruments and more specifically to drums. Drums are not the simple instruments that they may appear to be upon first consideration. Rather, a drum's musicality is a culmination of various elements. A foundational or principal factor that influences the sound of a drum is the shape of the drum shell, both in size or dimensions and in contour or configuration. Thickness of a drum shell wall may vary from drum to drum and may itself be based on various elements including, for example, structural considerations of the drum size and tonal considerations of the drum sound. The contour of a drum also impacts the tonal quality of the drum. Consider the differences between the tapered shell of a conga drum and the cylindrical sidewalls of what is commonly referred to as a “tom” or “tom-tom.”
On a more detailed or less conspicuous scale, that part of a drum which is struck in drumming, namely, a drum head skin or membrane that is stretched across a drum shell, its tension, its thickness, and its composition affect the tone and musicality of the drum. Further yet, that point at which the membrane contacts or interfaces with the drum shell, namely, the bearing edge, also affects a drum's tone. The drum shell wall edge may be formed with various contours and provide various drum tonal qualities, respectively. Three of various commonly known wall edge contours include a fully rounded symmetrical bearing edge, a rounded 45° bearing edge, and a chamfered bearing edge. The fully rounded bearing edge tends to boost middle to low range frequencies by providing maximum shell contact with the membrane. Middle to high range frequencies are boosted by a more focused bearing edge area for membrane to shell contact that is provided by a rounded 45 bearing edge, for example.
With the wall edge shaped and used as the bearing edge and with the wall edge in direct contact with the membrane, the bearing edge is an integral part of the drum shell and generally not subject to modification. Thus, beyond the apparent musical differences of different types of drums, conga, tom, bass, or snare, for example, a drummer requires multiple drums of each type or at least multiple drum shells to access for a given playing session the differing drum tonal qualities that result from various bearing edges.
Further, the interior shell wall surface may also influence a drum's tonal quality or sound. This is a well-recognized consideration, especially with regard to bass drums in which acoustic damping materials are commonly placed. In a simple form, the acoustic damping material may simply be a pillow placed within a bass drum. Alternatively, specifically designed fill materials may also be used. One factor that these damping techniques seek to address is the formation of standing sound pressure waves within the drum shell, which may or may not be desirable.